In the prior art, a shaped composite part with a thermoplastic matrix is achieved by hot stamping a consolidated laminated blank. When the reinforcing phase of said composite is made up of continuous fibers, forming the blank by stamping involves the inter-laminar slipping of the plies that make up the laminated structure of said composite. Such inter-laminar slipping is only possible if the matrix of said composite is in a sufficiently fluid state during the stamping operation. That state is achieved by heating the blank, prior to stamping, to a temperature above the melting temperature of the polymer that makes up the matrix of the composite. When the polymer is a high-performance thermoplastic polymer such as polyetheretherketone or PEEK, the heating temperature is high, commonly located between 350° C. and 440° C. That temperature must be reached throughout the volume of the blank to allow the slipping of the plies of continuous fibers and prevent the introduction of tension in the fibers, squeezing between fibers and waving of fibers, as those defects would have disastrous consequences on the mechanical properties of the part thus made. Thus, it is commonly accepted and experimentally observed that the blank to be made using the stamping operation must be free from defects such as porosities. That is because according to the experimental findings of the prior art, the presence of an air knife in the laminated structure, even over a short distance, creates uneven temperatures during heating, which defect leads to a point of fixation between the affected plies or fibers, which point of fixation locally opposes inter-laminar slipping. Further, the air knife collects the products of the gas released when the blank is heated and is not closed during stamping. Thus, in the prior art, the method for stamping a composite material with a thermoplastic matrix is based on the observation that any porosity in the blank will be present in the final part made by stamping the blank.
Thus, the stamping method according to the prior art is applied to nested blanks that are trimmed out of a consolidated plate, where particular care is taken to make said plate, which undergoes inspection that is as stringent as that of the final part, increasing the cost of the parts made using this method of the prior art. The document WO 2013/127965 describes a method for making such a consolidated plate.
The consolidation of a composite comprising a matrix made of thermoplastic polymer includes three phenomena:    one essentially mechanical phenomenon, which tends to create close contact between plies as a result of the pressure and viscosity of the polymer;    one essentially chemical phenomenon known as autohesion, which leads to the adhesion of plies to each other by the diffusion of molecular segments through the interface and then the whole thickness of the plies;    a polymer flow phenomenon, sometimes named impregnation, where the closed voids remaining in the material are filled.
The document FR 2 987 304 describes a hot stamping method for a composite material with continuous reinforcement, using a blank in a state known as the pre-consolidated state, obtained by placing fibers and partial autohesion between plies, that is to say adhesion of plies to each other over their entire contact interface, with no voids at the interface, where the segments of the molecular chains of the polymer making up the matrix diffuse over a very limited thickness between the plies on each side of the interface. That state is different from the state known as the consolidated state, where autohesion is large, where the molecular chains of the polymer making up the matrix extend and interlace over the entire thickness of the plies. Even though the method is an improvement on the prior art, it however makes it necessary for the quality of the blank to still be high, with a porosity rate below 1%. Also, the method is carried out at a high temperature, that is to say at a temperature above the melting temperature of the material, and so the impregnation phenomenon occurs and can reach that low level of porosity.
The document FR 2 922 276/WO 2010 0097547 describes a method for obtaining a shaped part using an assembly of unconsolidated plies. The method is not a stamping method, it is a method that can be assimilated with molding, as the unconsolidated assembly of plies undergoes a complete cycle of heating and cooling, including consolidation, inside a closed mold where a vacuum is applied to the cavity. Applying a vacuum to the closed cavity removes the air between plies. The productivity of such a method is modest compared to the stamping method and leads to very little or no inter-laminar slipping compared to the stamping method.